Finding the Fourth Proportional to 1,015.35, 1,400.61 and 642.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,015.35 : 1,400.61 = 642.18 : x
2. Step 2: Convert to fraction form
   1,015.35/1,400.61 = 642.18/x
3. Step 3: Cross multiply
   1,015.35x = 1,400.61 × 642.18
4. Step 4: Simplify right side
   1,015.35x = 899,443.73
5. Step 5: Solve for x
   x = 899,443.73/1,015.35
6. Step 6: Final answer
   x = 885.85